More so than any other steps that I take in my morning preparations, picking out clothes in advance saves me the most amount of time and frustration. For reasons I do not fully understand, trying to pick out clothes in the hour or so after I have woken up is an exercise of frustration.
Part of the problem is the lack of light in the morning. On most days during the school year, I am the first person awake in my house. I have to move around in the morning using a little light as I can to keep my wife from fully waking. Trying to pick out clothes in the dark is at the least frustrating and can sometimes even lead to some rather embarrassing choices.
However, even on days when I have slept in, and the morning light is shining, I still have difficulties when I haven't chosen clothes in advance. Some of that might have to do with how slowly my tired mind works. Perhaps it has to deal with being under a time constraint.
Whatever the reason, if I don't take steps to prepare my choice of outfit the night before, my morning just does not move as smoothly. Actually, I find that front-loading tasks usually works better for me than attempting them at the last moment. There's probably a lesson to be learned here, but I'm actively choosing to ignore it for the time being.